A little context - I already have some experience with Astrophotography; I have a Canon EOS 700D along with the kit lens & have just purchased a Samyang 14mm f2.8. I also own a Celstron AstroMaster 114 as well as the Celstron travel scope 70. I also recently got a t-ring for my canon...

I'm ashamed to say that I don't really have any experience using telescopes (looking to change that!) so I'm a complete beginner to using a scope as a camera lens, but it's something I have wanted to try for a long time.

To my delight & surprise, the travel scope does already have a t adapter that fits my canon t ring. So I'm assuming that this will enable me to use either scope now as a prime lens? Long story short - after some research today I nearly pulled the trigger on purchasing a t adapter from Amazon for £25, before checking my travelscope which already had one - but it's not quite the same. So my question is - will the t adapter I have allow me to use the scope properly as a lens?

Is the t-adapter you were thinking of buying this one with the built in Barlow?

That may be the one to get - though it won't guarantee that you can take images with your Astromaster. One of the problems/design features for Newtonian scopes is that the primary image is formed inside the focuser, so you can't actually get the image on the sensor of your camera. This means that the t-adapter from the Travelscope probably won't work on your Astromaster. However, one of the things the Barlow lens does is move the primary image forward - possibly out of the focus tube, so you may be able to capture it on your camera. I can't guarantee this though, so you may end up sending it back - though for Amazon at least, that won't be a problem.